Defensive publication



DEFENSIVE PUBLICATION UNITED STATES PATENT OFFICE Published at the request of the applicant or owner in accordance with the Notice of Dec. 16, 1969, 869 0.G. 687. The abstracts of Defensive Publication applications are identified by distinctly numbered series and are arranged chronologically. The heading of each abstract indicates the number of pages of specification. including claims and sheets of drawings contained in the application as originally filed. The files of these applications are available to the public for inspection and reproduction may be purchased for 30 cents a sheet.

Defensive Publication applications have not been examined as to the merits of alleged invention. The Patent Oflice makes no assertion as to the novelty of the disclosed subject matter.

PUBLISHED NOVEMBER 24, 1970 T880 007 PREPARATION OF PURI FIED AROMATIC ACID Olden E. Paris, Wilmington, Del., and Robert H. Sullivan,

Woodbury, NJ., assignors to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware Filed Jan. 15, 1970, Ser. No. 3,234 Int. Cl. C07c 51/42 US. Cl. 260-525 No Drawing. 7 Pages Specification Purified aromatic acid is prepared from an aqueous solution of an alkali metal salt of the acid which contains reducible impurities, wherein the alkali metal is selected from the group consisting of sodium, potassium, rubidium and cesium, by reducing the impurities by catalytic hydrogenation, followed by acidifying the solution to precipitate the purified acid. The process is particularly useful for preparing purified terephthalic acid, especially where the reducible impurities are salts of aldehyde acids such as para-formylbenzoic acid. The reducible impurities are hydrogenated by contacting the aqueous solution with hydrogen in the presence of a hydrogenation catalyst at a pressure of from to about 100, preferably to p.s.i.g., and at a temperature of about from 25 to 100 C., preferably 40 to C. Any of the known hydrogenation catalysts can be used, but preferred catalysts are nickel/kieselguhr, cobalt/kieselguhr, nickel/ aluminum oxide, active copper chromite, Raney nickel and chromium-promoted Raney nickel, with chromium-promoted Raney nickel being especially preferred. The amount of catalyst should be about from 0.5 to 3, preferably 1 to 2, percent by weight based on the amount of aromatic acid salt. The hydrogenation should generally be continued for about from 30 to minutes, with a slight excess of hydrogen over stoichiometric quantities being used to insure complete reduction of the impurities, 

